Part I. R& D Status - pcaarrd - Department of Science and Technology

et al. 1995). These aphids acquire and transmit
virus very quickly through sap feeding. It is still
unknown, however, whether the virus is
transmissible via the seed, but it may be seedborne
(Bajet 1996).
Bato et al. (1993) identified nine natural
enemies of aphids. These are coccinelid beetle,
syphid fly, chalcids, braconids, chrysopids,
staphylinids, mirids, hemerobiid, and
Entomophtora sp. (a fungus).
Scientists use serological assays, mechanical
transmission, electron microscopy, or a mix of the
three to detect PRSV-infected papaya. Using
serological assays, scientists confirmed that the
Philippine PRSV is identical to the viruses in
Thailand, Australia, Hawaii, and Taiwan (Bajet
1996).The PRSV strain was successfully isolated
in zucchini squash (Cucurbita pepo cv. Blackjack)
(Bajet 1997; 1996). Along with okra, corn,
mungbean, eggplant, cucumber, jelly melon,
pumpkin, squash, centrosema, ‘gabi,’ ‘upo,’
‘patola,’ ‘melon-melonan,’ and ‘balatong-aso,’
zucchini squash serves as an alternate host of the
vectors and the virus (Sumalde 1995). The isolate
produced the typical symptoms in both the squash
and papaya.
Similarly, the molecular variability of PRSV can
be known through cloning and deoxyribonucleic acid
(DNA) sequencing (Aquino and Valencia 2001).
Based on the entire cp gene sequences, isolates
from Bulacan, Cavite, Quezon, Isabela, and
Marinduque were identified at 97–98% sequence
homology. Scientists need to further verify isolates
variability and dendogram development based on
genetic coefficient to confirm the virus’ genetic
variability.
Planting PRSV-tolerant variety like the Sinta
papaya is one of the recommended practices to
manage PRS (Villegas 1996 a and b; Sumalde et al
1995; Bato et al. 1993). The Sinta papaya could
only serve as a stopgap measure in the absence of
resistant varieties. It must be combined with other
disease management strategies such as:
• Roguing or proper disposing of infected
plants;
• Controlling the vector by eliminating
alternate hosts;
• Intercropping with taller crops or by
spraying insecticides;
• Isolating plants;
• Subjecting plants into quarantine;
• Conducting proper cultural management
practices such as weeding, fertilization, and
irrigation during dry season; and
• Treating papaya as an annual crop rather
than as a perennial crop.
These disease management strategies were
being employed in the papaya rehabilitation and
development project in Southern Tagalog and in
the Bicol region (Sumalde et al. 1997; 1995). The
project also involved information, education, and
communication (IEC) campaigns through
consultative meetings, training-seminars,
and trimedia to enhance awareness of papaya
growers on PRSV and to strengthen linkages among
concerned stakeholders. The IEC materials of this
project were supplemented with other publications
from other researchers in the NARRDN.
In Davao, Pableo et. al. of BPI-Davao National
Crops Research and Development Center (BPI-
DNCRDC) suggested practical steps to control
spider mites. These include inspection, judicious
spraying with formetana, and removal of
nonfunctional leaves.
Modified Atmosphere (MA) Storage
and VHT of Solo Papaya
Postharvest Training and Resarch Center
(PHTRC) researchers’ findings on the postharvest
handling of papaya focused mostly on the Solo
variety. Serrano (1996) optimized the application
of MA storage of the Solo papaya to delay ripening
during commercial shipment trials from Misamis
Oriental to Laguna. On the other hand, Lizada
et al. (1991) determined the effect of VHT on the
ripening characteristics, fruit injury, and disease
incidence on the Solo papaya.
18 ............................................................................................................. R&D Status and Directions